Wednesday, October 27, 2010
Fossil of the Week
10/27/10 – Moa Pelvis
The moa are a group of extinct flightless birds found only in New Zealand. They belong to the ratites, a group of flightless birds including living members on four continents: the emu (Australia), the ostrich (Africa), the kiwi (New Zealand), the cassowary (Australia and New Guinea), and the rhea (South America). The moa, however, are distinctive from all other known ratites, and in fact all other birds, in lacking wings entirely.
There were probably ten to fifteen species of moa upon the Earth. The number of species names, however, exceeds the actual number of species because the two sexes were often mistakenly named separately, principally because females were significantly larger than males. Moa lived in a wide range of areas from the coasts to the mountains of New Zealand and ranged significantly in size, the largest being around 2 meters (6.5 feet) at the hip. Preserved gizzard contents consisted mainly of tree material, suggesting that they lived in forests. Most known moa specimens are subfossils rather than true fossils (still consisting of bone, not rock), and there are even some dried and one mummified specimens known, allowing paleontologists the opportunity to extract DNA for some species.
Moa became extinct at least 600 years ago due to human hunting. Prior to humans’ arrival on New Zealand, it is thought that their only predator was the enormous (and now also extinct) Haast’s Eagle. At least 40% of New Zealand’s endemic species have become extinct since humans arrived on the islands.
Pictured here is the extremely robust pelvis of a moa (Emeus crassus, PRI 50004-50005) viewed from the ventral side (the underside). The pelvis is a compound bone – a fused combination of several vertebrae, the ilium, ischium, and pubis bones. PRI has a large number of bones from this moa specimen and the skull, jaw, and one of the leg bones can be seen on display in the Museum of the Earth. Most moa bones are large, as they are necessary to support the immense weight of the bird, but the skull is significantly more fragile and a much rarer fossil find.
Text by Ursula Smith (reprinted from “Fossil Focus” in American Paleontologist, Fall 2010).